R1193Q of SCN5A, a Brugada and long QT mutation, is a common polymorphism in Han Chinese

Recently, Wang et al 1 reported R1193Q mutation of SCN5A in one of the seven patients with acquired long QT syndrome (LQTS) and suggested that R1193Q is a functional mutation that can increase the susceptibility to this syndrome. The mutation destabilised channel inactivation and generated a persistent late current. The investigators found that 0.2% (4/2087) of the control subjects (of whom more than 90% were white and only 0.4% were Asian) also carried the mutation, and they suggested that it may be a risk factor for LQTS in the general population. The same mutation (listed as R1192Q using SCN5A RefSeq: NM_000335) has been reported in a Japanese infant with Brugada syndrome with frequent episodes of ventricular fibrillation.2 They found that none of the 100 control subjects of Asian descent carried the variant. We have identified the same R1193Q mutation by direct DNA sequencing of SCN5A in a four generation family of Chinese descent with cardiac conduction …